1. Field of Invention
The present invention relates to a touch panel, and more particularly to a touch panel which can reject a noise.
2. Related Art
Recently, the technology of a touch panel is developed quickly. For example, resistance type touch panel, capacitance type touch panel, sound wave type touch panel and optics type touch panel have been widely applied to communication products, computer devices and consumptive electronic products so as to further increase the efficiency and convenience of the applied electronic product.
The optics type touch panel can input a signal by a finger so as to have convenience of input operation, wherein the input operation does not need to press the touch panel. Thus, this touch panel has no disadvantage of a stress caused by repeatedly touching the touch panel, and a damage caused by deformation. Also, this touch panel has simple constitution, less components, and high yield rate of the product so as to decrease the cost by suitably using the mass production.
FIG. 1 is a view showing a basic constitution of conventional touch sensor 100. A glass substrate 110 and an indium tin oxide (ITO) layer 130 are boned by an optically clear adhesive (OCA) 120 located therebetween. Furthermore, the indium tin oxide (ITO) layer 130 and a cover lens 140 are boned by another OCA 120 located therebetween, thereby finishing the touch sensor 100.
FIG. 2 is a view showing a basic constitution of conventional touch panel 200. A touch sensor 100 is disposed above a liquid crystal display (LCD) module 250 so as to finish the touch panel 200. For example, the glass substrate 110 of the touch sensor 100 is bonded to the LCD module 250, and there is an air gap 260 between the LCD module 250 and the glass substrate 110.
FIG. 3 is a block diagram showing signal processing of the conventional touch panel. During touching, a touch sensor 100 senses variances in capacitance value and then outputs an analog signal to an analog multiplexer 320. The analog multiplexer 320 outputs the scanned analog signal to an analog/digital converter 330 by means of a scanning action. The analog/digital converter 330 converts the analog signal to digital signal, and then outputs the digital signal to a microcontroller 340. The microcontroller 340 processes the digital signal, and then outputs a control signal. Finally, the control signal transmitted to an operating system 360 through an interface 350 so as to calculate and then determine a touch position.
However, after the touch sensor is installed on the LCD module, a noise generated by the LCD module interferes with the touch sensor so as to cause the touch panel to wrong determine the touch position. The noise is resulted from the couple effect between a common voltage of the LCD module and data lines, e.g. particularly in a heavy loading picture or fast renewed picture so as to cause the picture to be unstable. Recently, a general method is to adjust a firmware so as to solve the problem of wrong determining the touch position. For example, the frequency that is converted from analog to digital is adjusted, and an algorithm of the microcontroller for processing signals is adjusted. However, this adjusting method will extend the processing time of the sensing signal from touch sensor to the operating system.
Therefore, it is required to provide an anti-noise touch panel capable of solving the forgoing problems.